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"It seemed to be an unusual request, but I know that this is something Katie is passionate about and it's an important thing to do," Kimmel said. "So, with that said, we're about to watch a camera go where no camera has ever gone before."

Fighting colon cancer is near to Couric's heart. Her first husband, Jay Monahan, died of colon cancer in 1998. To help encourage others to get colonoscopies, Couric underwent a live screening on Today nearly two decades ago.

Couric guided Kimmel every step of the way. She mixed him a pre-screening "cocktail" to clear out his colon, drove him to the hospital and gave him a pep talk before the procedure.

Of course, the comedic host managed to keep things light. He changed into a formal gown instead of a hospital gown before the colonoscopy and made his doctor play a round of Operation to test her skills.

"That was good. I feel comfortable now," Kimmel said after his doctor successfully extracted a butterfly from the body of the Hasbro game.

Jokes aside, Kimmel took the colonoscopy seriously and underwent the procedure. So, did the doctors find anything alarming?

"We found your keys, some [toy] soldiers--you've been looking for those haven't you?" Couric teased, showing him the loose items. "And best of all, look, we found your harmonica, Jimmy."

Thankfully, Kimmel's colon was free of any polyps and he won't have to have another screening for about 10 years.

"Thank you, Katie, for invading my colon," he said.

Couric teased she had a "colonoscopy mystery date" before Tuesday's episode.